text:
How high can a ramjet go?
Yesterday, there was an off-topic question on Space.SE, asking if a ramjet-missile could place itself in orbit. Impossible for a ramjet, obviously, as it requires a high speed flow of air and is too slow to reach orbital velocity.
However, this got me thinking about a ramjets altitude limitations:
How high could a ramjet-powered aircraft or missile possibly go? And how does the speed the jet is traveling at effect the highest possible altitude?

Jets of all kinds need enough oxygen outside. The highest a jet has ever flown was 37,650 metres (123,520 ft) by a MiG-25 in 1977. That was however a very parabolic flight. In leveled flight jets can fly at 90,000 ft (27 km) highest, as yet.

Conventional ramjet or scramjet?

You might want to look into Shcramjets as well.

Is bringing your own air considered cheating, for the purposes of this question?

@Flater yeah i'd say that is cheating... that would kinda eliminate one of the primary reason why we use ramjets at all (especially in missiles), the fact that they do not need to carry any air themselfes, which leaves more room for burning fuel...

@Flater sort of relevant: "Propulsive fluid accumulator". Scoop up air while IN ORBIT?

Even more relevant: Airbreathing satellite thrusters!

This is under current research, a Ramjet while inside atmosphere, a pure rocket above, this could bring things into orbit at a reduced fuel cost. The french magazine 'Science&Vie', published a good article about: 'Le pari fou de l'avion orbital' ('The fool bid of orbital airplane', July 1986) Salut +

Here's a quick estimate for this.
The maximum altitude for level flight is when the engine can't produce the thrust required to fly fast enough to generate the lift required to balance the weight.
Ramjets work best at around Mach 3 and can operate up to Mach 6
Lift is proportional to speed squared and air density. So doubling the speed allows the plane to fly in air that is a quarter of the density.
The equations for calculating air density with altitude are moderately complex but there are a couple of tables here that show that the density at 32km is about eight times less than at 20km.
So if the SR-71 flew at Mach 3 and 25km, and if you could make a SR-71 that could fly at Mach 6, it might manage another 5 or 10 km in altitude.
Obviously that's a massive simplification because if switching engine technologies would have improved the SR-71's speed, they would have done it. Also because the SR-71 engines were ramjets when it was flying fast.
A ram jet won't get you into orbit because orbit is not just a matter of flying high enough but of reaching orbital speed - the speed where the curve of your naturally falling trajectory will miss the earth due to the earth's curvature. It's about Mach 25. And (as Ross points out) even if you could reach Mach 25, you can't circularise the orbit with an air breathing engine because that requires thrust at the highest point.

At those altitudes you also have to take temperature into account. A fixed Mach number is not going to give you a fixed TAS due to the temperature dependency of the speed of sound.

@Bianfable - yes, it would really help if someone who understood the calculations better could work it out more accurately.

I could do the calculations more accurately, but I don't think that would really answer the question. This is more of an answer to how high could the SR-71 fly if it could go to Mach 6?, but the original question was about a ramjet in general (or a "ramjet-missile").

You can't reach orbit with an airbreathing engine.  Even if you can get fast enough and high enough, you can't circularize your orbit once you're outside the atmosphere if your engine requires air. And a ramjet just can't go fast enough to escape Earth entirely.

Wouldn't air density be a limiting factor with respect to generating thrust? Where is that ceiling?

NASA indicated X-15 did well with a Ramjet and external fuel tanks added, but drag reduced top speed to Mach 5, when more than Mach 6 were envisaged. When the X-15 flew at Mach 6.7, aerodynamic rub heat was so huge, that several parts were just carbonized. Materials evolve fast, so does aerodynamics. Let's wait and see. Gesund +

@user2647513 - density isn't really the limit, because it reduces both lift and drag, so you can fly faster with the same thrust and generate the same lift. The limit is the maximum speed for the engine. You're flying so fast that air doesn't have time to mix with fuel and burn it, and slowing the air down would cause too much drag.

Ramjets can fly at least this high:
Scramjet, X-43A flown in 2004: 110,000 feet / 33 km.
Ramjet, RJ43-MA-11 on a BOMARC B missile, 1961, 100,000 feet / 30.5 km (photo caption, p. 31).
(Ramjet, XRJ47-W-5 tested by NACA in 1955: 73,000 feet / 22 km.)
Ramjet, extrapolated from data for flights where the vehicles were still accelerating when they ran out of fuel: 131,000 ft / 40 km.  (One flight coasted to 151,000 feet, but that's probably not what's being asked here.)

...if ramjets can continue to accelerate in an environment where the air density is under 20 g/m3, then perhaps they can sustain powered flight to 40 km, where the density is only 4 g/m3.

The SR-71 (with engines in ramjet mode at altitude and speed) routinely flew higher than 22 km -- it was operational at about 81000 (roughly 25 km) at Mach 3 for many years.

Yes, but I found only unresolved debate about whether its "turbo ramjet" engines really count as ramjets.

Bomarc missile (B series) had a maximum cruising altitude of 100K ft.  It was initially launched with a rocket engine, but titled over and cruised with a pair of ram jets

SR-71 engines may act as turbojets or ramjets depending on airspeed, I'd say. Blessings +

[ Orbital Airplane, Science&Vie, Jul 1986]
Thrust and efficiency of Lorin Ramjet (Report by Sänger and Bredt) increase with the square of speed, with the square root of combustion temperature. Ramjet start working around 300 km/ h, studies considered 300 m/ sec airspeed. Yield circa 12'000 HP per square meter of main bulkhead area. At higher altitudes, (calculations were made for a top speed of 0.9 Mach and 12 km ceiling, intended in a pursuit airplane, engineers thought Lorin Ramjet would not work above 18 km, because of poor combustion), thrust and propulsion power decrease, slightly less than density of air, but propulsion coefficient and efficiency increase because of lower temperature of fresh incoming air.
At ground level and 300 m/ sec airspeed, thrust is 3'000 kg per square m of bulkhead area. Range increases from 367 km at ground level, in a case, Skoda-Kauba P.14?, proposed in https://www.enginehistory.org/Rockets/LorinRamjet/LorinRamjet.shtml to 1'100 km at 18'000 m.
Duration of flight for a given fuel load was maximum at 14'000 m height, decreased slightly above this, for a 6'000 kg total airplane weight, 1'000 kg payload, 2'400 kg of fuel, wing area 30 m2. Athodyd operating at higher temperatures losses efficiency, smaller athodyd impose higher working temperatures.
Propulsion power increases with third power of speed.
They advised 2 m diameter Ramjets. Minimum speed at which diving is not needed to accelerate, at 12'000 m height, was 430 km/ h. Test of this tube on conventional airplanes were conducted at 100 m/ sec over a Do-17Z, then 200 m/ sec airspeed. For the design considered, speeds were 1'100 km/ h at ground level, and 950 km/ h in mid stratosphere.
I've suggested having a Pulse Jet inside or side by sides of the Ramjet, Athodyd tube diameter modified accordingly, pulsejets provide power at zero airspeed, and could carry Ramjet to its start speed. Intake duct angle was determined being best at 10º. Inside a duct, heat form outer parts of pulsejet would be added to thrust; if a double duct wall is installed, same would happen with heat of outer side of ramjet.
OK?
Blessings +

So the short answer is "18 km, theoretically."

Perhaps, but about added information, you never know when it will be useful. Besides this generic comment, info I've added comes from WW II times, situation has changed, 'Hypersonic Ramjet' may not differ too much from these Lorin tubes tested. Thanks. Blessings +

Ramjet Thrust is produced by passing the hot exhaust from the combustion of a fuel through a nozzle, it accelerates flow, the reaction to this produces thrust. To maintain  flow through nozzle, combustion must occur at a pressure higher than pressure at the nozzle exit. In a ramjet, high pressure is produced by "ramming" external air into the combustor using the forward speed of the vehicle.

The external air brought into propulsion system becomes the working fluid, like in a turbojet. In a turbojet engine, the high pressure in the combustor is generated by a piece of machinery, a compressor. There are no compressors in a ramjet. Therefore, ramjets are lighter and simpler than a turbojet. Ramjets produce thrust only when the vehicle is already moving; ramjets cannot produce thrust when the engine is stationary or static.

Since a ramjet cannot produce static thrust, some other propulsion system must be used to accelerate the vehicle to a speed where the ramjet begins to produce thrust. The higher the speed of the vehicle, the better a ramjet works until aerodynamic losses become a dominant factor.

The combustion that produces thrust in the ramjet occurs at a subsonic speed in the combustor. For a vehicle traveling supersonically, the air entering the engine must be slowed to subsonic speeds by the aircraft inlet. Shock waves present in the inlet cause performance losses for the propulsion system. Above Mach 5, ramjet propulsion becomes very inefficient. The new supersonic combustion ramjet, or scramjet, solves this problem by performing the combustion supersonically in the burner.

Because the ramjet uses external air for combustion, it is a more efficient propulsion system for flight within the atmosphere than a rocket, which must carry all of its oxygen. Ramjets are ideally suited for very high speed flight within the atmosphere.
EngineSim is an interactive Java applet which allows you to test the design of ramjet engines. Fundamentals of ramjet engine propulsion with can be learnt with EngineSim simulator.
Orignal by Nancy Hall, NASA 'Ramjet Propulsion'. Blessings +

There is a good review about Hypersonic flight in the french magazine 'Science&Vie', nº 826, July 1986. Salut +

Wikipedia, for Lockheed X-7, Ramjet powered drone, tested in the 50s, basis for Bomarc, indicates a top speed reached of Mach 4.3, height of 32 km, 106 thousand feet., outperforming missiles. Thus, other published information could be misleading. Blessings +

Comments on a Q&A site are for improving answers, not for long conversations.  I invite you to move the new information you've found into the answer and to delete the comments.

Wikipedia's page for the X-7 mentions only its specifications, not its measured performance.  And the webpage it cites for that has vanished :-(.

I am not responsible, and have no way to influence the Quality or operativity of Wikipedia data and links, please contact them, or add info from yourself. About the Boeing 'Bomarc', I have no access to actual data about performance from Boeing nor USAF. Please check this with them, also. Thanks. Blessings +


text:
Is it possible to build an ultralight helicopter with electric motors as its main engines?
So I'm trying to make an electric ultralight helicopter, but I'm not sure if it will work. Is it possible to use electric motors to make it fly? If yes, I'm going to need some advice.
I'm expecting the aircraft to be able to lift a 200kg load, with the maximum rotor blade diameter of 7m in coaxial rotor configuration.

There are companies (Uber, amongst others) building electrically powered aircraft with VTOL capability (example), so the answer to your question is 'yes'. However, those companies are using drone-like technology to drive multiple rotors and use that for stability and control. This has a number of advantages and specifically avoids the complexity of a rotor head. Do you really want to build a helicopter?

Yes, but with current battery technology it won't stay up for very long.  The problem is twofold: the batteries can only hold so much power, and they can only output it at a certain maximum rate.

From a quick Google search, you can find that Sikorsky Firefly and Tier One R44 are two examples of eHelos, conventional helicopters converted to electric propulsion. They both fly around 20-30 minutes (though the Firefly never flew).
As for building an electric helicopter, I believe off-the-shelf components (such as Tesla motors and batteries, available from parts breakers) have enough performance for an eHelo. The actual configuration of the aircraft (single main, coaxial, multicopter etc.) depends on the manufacturer's expertise on rotor blade hubs and/or distributed electric propulsion. So unless you work for Kamov, a coaxial rotor hub will be prohibitively complex (thus expensive) for a prototype ultralight helicopter.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
How would a fighter be changed from having static stability to having relaxed stability?
A good portion of aircraft, especially those designed before the 1970's, possessed static stability. However, modern fighters (and some airliners) have been build with relaxed static stability.
This question was aroused by the book Designed for the Kill by Mike Spick. On page 119, it states (in reference to the Shenyang J-8 II Finback B):

In 1991 improvements were stated to be in hand to improve subsonic manoeuvrability, and one of the obvious moves would be to introduce variable camber by using leading edge slats. There can be no doubt that FBW and relaxed stability would also benefit it considerably, while weight reduction could be achieved by the use of composites.

How would a fighter such as the J-8 physically be changed to change the centre of gravity in relation to the centre of lift? Would the wings be resized/moved? Would the tailplane be made smaller? Would internal items be shuffled around to put heavier ones at the back? Or could some sort of clever aerodynamic device be added to modify the airflow somewhere?

The first and most important step is to move the center of gravity back relative to the neutral point of the configuration. This is done either by shifting masses on the airframe back or by shifting the wings forward. This needs to be complemented by the addition of a multiple redundant and fast flight control computer.
Now the tail will add lift instead of downforce, so the wing area required for manoeuvring and take-off/landing can be reduced. Or performance improves - compare the minimum speed of the Mirage III to that of the Mirage 2000.
To see how much the wing area could be reduced, here is a comparison drawing of the regular SEPECAT Jaguar with one designed for the same requirements, but with relaxed stability (copied from this answer). The forward shift and reduced area of the wing should be obvious.

Comparison of conventional Jaguar (top half) and CCV version (bottom half) by Ray Whitford.
What is done to a specific airframe depends on the objectives for the move to relaxed stability: This could be much better supersonic range or better short field performance. For the first you will shrink the wing, for the second you better keep wing size but move it forward and heavy items back. The change from the one engine of the MiG-21 to two more powerful engines certainly helped to shift the center of gravity of the J-8 back.
Usually all of the methods you mention are used in combination (except for the clever aerodynamic device, unless you mean a sophisticated FCS):

The wings are resized/moved
The tailplane would be made smaller
Internal items will be shuffled around or exchanged to shift the center of gravity further back.

I don't have access to the book, but the improvement mentioned in the quote is

... leading edge slats ...

Slats wouldn't change the center of gravity noticeably. Your Wikipedia reference doesn't currently mention slats. Perhaps you intended to say "change center of lift/pressure". The main goal is improve maneuverability, which can be achieved various ways.
This reference:
https://en.topwar.ru/24868-shenyang-j-8-ii-finback.html
includes the following text:

Acceleration characteristics and maneuverability were enhanced by the
use of maneuverable slats, as well as more powerful engines WP13B.

You also asked:

How would a fighter be changed from having static stability to having relaxed stability?

Of course, the aircraft can be designed that way from the start. To increase maneuverability, negative-dihedral, or anhedral can be included in the design, but that is not adjustable during flight.
Other options would include:

Speed/Dive Brake:
Vectored thrust:

Next Question:

How would a fighter such as the J-8 physically be changed to change
the centre of gravity in relation to the centre of lift?

I don't see any documentation that says it could. (Burning of fuel in tanks laterally displayed will do that a bit). More effective and easier to change camber with controls like slats.

Would the wings be resized/moved?

They can:
https://en.wikipedia.org/wiki/Variable-sweep_wing
But the J-8 isn't part of that club.

Would the tailplane be made smaller?

Dynamically? not that I'm aware of.

Would internal items be shuffled around to put heavier ones at the
back? Or could some sort of clever aerodynamic device be added to
modify the airflow somewhere?

Moving heavier objects around, no.
Aerodynamic device, yes. As mentioned slats.
Besides flight controls, my reference also said more powerful engines.
Your reference mentioned composites, which reduce weight and can allow tighter turns.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Do any modern aircraft require 3 crew on the flight deck?
These days, most (all?) airliners require 2 pilots at any given time. However, until the 1980s, many airliners required more crew on the flight deck than this (5 for the Lockheed Constellation and 3 for the 747 models). The AN-225 (first flight 1988) is unique in having 6 flight crew members (related).
I'm interested in knowing if there are any modern aircraft (airliners and other types) that require 3 or more flight deck crew. For the sake of the question, let's limit "modern" aircraft to those which first flew after the year 2000. Spacecraft and spaceplanes don't count - atmospheric vehicles only. Sometimes there are more than 2 pilots on board for long-haul flights, but I'm interested in the minimum flight crew for the most basic flight.

I guess I'm asking about "certification" - what I'm interested in is the minimal amount of pilots required for the simplest flight. I'll try and edit the question to make it more clear

The terminology used in the Type Certificate Data Sheet is "Minimum Flight Crew". Example for the Boeing 747: "Minimum Flight Crew: Three (3): Persons (Pilot, Co-pilot, and flight Engineer)"

You write "airliner" in the example, but "aircraft" in the question. So, is it only about civilian airliners, or can we count military aircraft as well (which might have a radar/weapons/EW equipment operator)?

The Stratolaunch needs three crew and flew once for the first time in 2019, but it's not an airliner.  Agreed we need to know what you're asking about - airliners or aircraft?  Does the TTS-IS count?

There was like an Outer Limits episode with a trans-atlantic flight arriving westbound and failing to make contact with any of the usual radio points; Gander, Moncton, Halifax. Spoiler, they'd gone back in time and on descending saw dinosaurs in tropical jungles. Anyhow, there was a whole cast of characters in the cockpit: Captain, First Officer, Engineer, Radio Operator, Navigator, maybe a standby guy in a jumpseat, and of course a flight attendant coming and going with reports from panicked passengers (never themselves on screen). A whole stageplay just in an airplane cockpit.

@vsz, (and J. but I can only notify 1 user) When I asked the question I was only thinking about airliners but other aircraft are welcome and would certainly be more interesting.

@J... You should add the Stratolaunch as an answer. It looks like it requires 3 crew (2 pilots and flight engineer) and it certainly counts as an aircraft.

I don't think there is any aircraft designed since 2000 which requires a flight crew of more than two people.
It's hard to prove a negative, but historically only larger aircraft required more than two crew members in the cockpit. So I went through the Wikipedia articles of Airbus, Boeing, Embraer, Antonov, UAC (Ilyushin, Irkut, etc.) and Comac and looked for mid- to long-range aircraft that first flew since 2000:

Aircraft Model
First Flight
Crew

Airbus A380
2005
2

Airbus A350
2015
2

Airbus A310 MRTT
2003
3 or 4

Airbus A400M
2009
3 or 4

Antonov An-148
2004
2

Boeing 787
2009
2

Boeing KC-767
2005
3

Boeing P-8
2009
2 to 7

Comac C919
2017
2

Embraer C-390
2015
2

Ilyushin Il-112
2019
2

Ilyushin Il-276
2023 (planned)
3

Irkut MC-21
2017
2

The crew number is taken from the respective Wikipedia articles (where available). There are 4 aircraft that list more than two crew members here:

Airbus A310 MRTT: Wikipedia says

Crew: Three (hose and drogue) or four (flying boom) flight crew (two pilots and other flight crew)

and I found this article saying

The multi-role tanker transport is operated by a flight crew of three for all missions relating to Air-to-Air Refuelling (AAR): two pilots and the AAR operator. The AAR operator station is located in the cockpit just behind the captain. The two pilots have direct access to the majority of the information and controls concerning the AAR operational and safety aspects.

So, technically, the AAR operator(s) would count as crew in the cockpit. However, you asked for "the minimum amount of flight deck crew for the most basic flight" and I guess the aircraft can be flown with just the two pilots, if no refueling is performed during the flight.

Airbus A400M: Wikipedia says

Crew: 3 or 4 (2 pilots, 3rd optional, 1 loadmaster)

so 2 pilots are enough and (even though listed as required crew) I wouldn't count the loadmaster as flight deck crew. I guess an empty A400M would be allowed to fly without a loadmaster on board.

Boeing KC-767: Wikipedia says

Crew: 3: 2 pilots, 1 boom operator

so this is similar to the A310 MRTT.

Ilyushin Il-276: While the Wikpedia article lists the crew as 3, the Ilyushin website on the planned Multi-Purpose Transport Aircraft (MPTA) says

Crew, persons: 3 (2)

and when further reading the article, it says

The flight crew includes three persons: chief pilot, co-pilot, and navigator. The aircraft design envisages installation of an additional seat for the flight engineer. [...] The aircraft design ensures autonomous (without contact with the home airfield) solving of transportation tasks and flight preparations by the efforts of technical and flight crews from 2 to 6 persons.

This sounds like up to 4 crew members can be in the cockpit, but only 2 are required.

«pilots» and «flight deck crew» are not synonyms.
«pilots» are subset of  «flight deck crew».
There have always been only two pilots flying the aeroplane, PIC and second officer, even in pre-«modern» times, according to your terminology.
Automation and computers rendered flight engineers obsolete.
Advancements in navigation like aviation-grade GNSS, virtual VORs, PBN etc made flight navigator obsolete.
There isn't any post-2000 design that requires minimum flight crew of more than 2.

Minimum pilot crew of no more than 2 has been long before 2000. And no, there isn't any post-2000 design that requires minimum flight crew of more than 2.

"There isn't any post-2000 design that requires minimum flight crew of more than 2", is it your opinion or do you have some reference?

«is it your opinion or do you have some reference?» - I checked all known non-military airplanes designed after 2000 and didn't find any with flight deck crew requirement of more than two.


text:
Hydrogen as fuel for jet engine or afterburner
Why is hydrogen not used as fuel for fighters? I understand that hydrogen engines are not yet developed but why is there no research going on in that file.
Can't hydrogen be used in specially designed afterburners?
After all, is has like 3 times the energy density of aviation fuel.

One part of the reason: while hydrogen has a high energy density, is has a much lower physical density, meaning that a tank of hydrogen with as much energy as a tank of jet fuel will be much larger. This makes for a heavier tank shell, and takes up more space inside the plane, displacing weapons and computers or forcing a bigger airframe.

https://aviation.stackexchange.com/questions/18809/are-there-any-programs-to-build-a-hydrogen-powered-airplane

perhaps not now but in the future is there a possibility that the turbines of the jet engine can be rotated by electric motor and hydrogen can be used to heat the air inside the turbine to increase pressure?

Not sure about the electric motor - the batteries powering it might be too heavy. You could use a generator make electricity for the motor, but then you'd need something to spin the generator.


text:
What are these crevices below the wing of B-52 bomber?
What are these crevices below the wing of B-52 bomber?

These are electronic countermeasures dispensers, more specifically chaff dispensers. You can see them in this walk-around, where an Electronic Warfare Officer shows them (timestamp 01:10:35).

That is a B-52H. The ailerons, which would have hinged at that location of the wing, were removed from later models of the B-52, including the -G and -H models.Those rectangular holes are outlets for radar-decoying chaff dispensers, and this is true for both the B-52G and -H models. Chaff consists of small shreds of metal similar to but thinner than aluminum foil.  The idea being that if the bomber was targeted by a radar-guided missile,  the aircraft would turn hard in one direction while ejecting chaff from the opposite wing, leaving a nice big radar target behind for the missile to hit. It's pretty effective, but less so on modern smart weapons.


text:
Why there are multiple classes in same plane?
This question always baffled me, why most conpanies do not have different planes for each ticket class ?
There are obvious benefits to this system:

Better paying customers can fly more reliable/newer/well maintained planes.
Economy class can mean economy for company too. Economy class will enjoy accessible prices by flying less maintained plane or plane with one engine not working. And maintenance is expensive.
More space for luxury, e.g pool, billiard tables, spa, jacuzzi, casin.
Safer travel, better paying client can have stuff that is normally not considered bacause of high cost, eg individual parachute per passenger.
Super economy class, ultra cheap, no frills plane, passengers and baggage share one big compartment, baggage is fastened to floor with rope, while passengers have to clutch some kind of handrail (not unlike bus) during landing/takeoff.
Seats take significant weight that could be used for extra passengers.
Novelty and dangers of super cheap flight could attract thrill seeking customers.
Seatless planes could have novel or extreme onboard entertainment. E.g is cock fighting or dog pitting still illegal over international waters ? Passengers could make bets. What about underground boxing ? Winner gets first class voucher.
Customised worst case gurantees, e.g if you crash we promise to look for you X days.

"Seats take significant weight that could be used for extra passengers."  This statement by itself earned my downvote...

I’m voting to close this question because it would fit better on travel.SE

"while passengers have to clutch some kind of handrail (not unlike bus) during landing/takeoff." I find it hard to believe you've ever been on a commercial airliner if you make statements like that...

I love this question.  Also, super economy fares will travel in planes with stub wings.  Usually down freeways or interstates.  Full wing spans cost more to produce and maintain thus only full fare passengers should have access to them.

This made me laugh so if you're trolling then thank you. If you're serious then.... oh boy.

These flights without cockfighting are a real killer.

I will try to answer this question by the bullet point you ask
> Better paying customers can fly more reliable/newer/well maintained planes.

The plane at the current status is as well maintained as it could be. You can better maintain the plane to increase reliability but at a huge cost with little improvement. Is that worth it? No.
> Economy class can mean economy for company too. Economy class will enjoy accessible prices by flying less maintained plane or plane with one engine not working. And maintenance is expensive.

Why don't 747s use unreliable, but cheap, jet engines instead?
In short cheaper stuff gets you no where. Twin engine plane with one not working is going no where. Plane that often breakdown goes no where. It will incur more cost to the airline to rebook passengers to another flight, provide them meal and accommodations as needed. And would anyone book a flight that has breakdown reputation? In the long run it is cheaper to have a reliable plane that depart on time and does not breakdown in flight.
> More space for luxury, e.g pool, billiard tables, spa, jacuzzi, casin.

Do they want that kind of luxury? 747 in the past had that luxury but it was removed? A380 had on board lounge in some configuration but not all. Some planes offer shower on board but not all. Why? Because this kind of luxury cost more than it is worth. A single person jacuzzi I found online has capacity of 180 litre which means 180kg of water alone. That is the weight of 2 passengers. You can call that the cost of luxury but do you want to pay for the cost of 2 passengers just for the water? I’m not sure.
•   Safer travel, better paying client can have stuff that is normally not considered bacause of high cost, eg individual parachute per passenger.

Why are commercial flights not equipped with parachutes for the passengers?
Parachute is not a magic wand that you just whip and it will work. You need proper training to wear it properly. You need the plane to fly smooth enough to jump out of. You risk breaking your leg when you land. And worst of all you are paying for high cost item that you are not likely to use since you have an already well maintained plane.
•   Super economy class, ultra cheap, no frills plane, passengers and baggage share one big compartment, baggage is fastened to floor with rope, while passengers have to clutch some kind of handrail (not unlike bus) during landing/takeoff.

You need to certify this with civil aviation authority. Good luck with showing them how can this be safe for all age group and sex.
•   Seats take significant weight that could be used for extra passengers.

???????
•   Novelty and dangers of super cheap flight could attract thrill seeking customers.

Dangers bit caught me immediately. Here we are providing air travel service. We provide safety. If there is any bit of danger the airline will try to improve it, I hope. If you want danger please do it on the ground or in aerobatic plane.
•   Seatless planes could have novel or extreme onboard entertainment. E.g is cock fighting or dog pitting still illegal over international waters ? Passengers could make bets. What about underground boxing ? Winner gets first class voucher.

I’m quite sure cock fighting or such is not illegal over international water but the plane is bound to the law of country of registration no matter where they are. So unless you can find a way so that passenger can be outside of the plane to bet on such this you can bet this to be illegal. And if this can be done what are you trying to operate? A flying casino? Good try man.
•   Customised worst case gurantees, e.g if you crash we promise to look for you X days.

This kind of guarantees is already provided in the current contract of carriage. In summary the airlines already promise to fly you from one place to another on the date and time you book for. They will do their best if there is unfortunate event occur. Usually if the plane crash they will cover the cost of treatment and if they fail to do it is a very bad airline. Will you trust to fly with airline that crash and make you pay the hospital bill?
In short it may not worth it to separate plane in to different class to justify the cost of operating it when you can have a different class on the same plane and operate it efficiently. There is an example of Singapore airline that operate an all-business class plane for Singapore-New York route but that is because the plane need to be lighter to carry more fuel for the route so they cannot carry all economy passengers. Other than that I cannot find the reason why would you want to operate the plane the way you explain.
Read more:
Why 1st and 2nd class but not fast or slow airplanes?


text:
Why didn't the airlines try to start copying SpaceX by putting camera on the outer body of the airplane?
This week my country Indonesia just had an Airplane crash accident Sriwijaya Air SJ182.
I'm getting sick with people speculating why or how the plane crashed. Well, we can wait for the black box analysis, but that will took quite a long time before we know how the plane crashed.
And the visualization of the crash accident will always end up the same. Speculating how it crashed based from data in the Black box.
Why can't we just put several cameras in the body of the airplane? I know there are clouds, rain water, lightning strike, and thunderstorm (can't we protect/shield the camera?)
Basically I wanted to ask the same as this question here :
Why don't airlines have in-flight video recordings like buses do?
(but I mean more like "record the flight from outside instead from the inside")
Now look at SpaceX Falcon9 rocket launches that had become very routine. They always have cameras. I'm sure Falcon9 Rockets also passing through Clouds,  rain water, Thunderstorm and lightning strike just like the Airplanes... SpaceX cameras just works fine even to the outer space.
So, I was thinking, like the title suggest, "Why didn't the industry start copying SpaceX method of putting a camera on the body of the Airplane so we could see how an airplane crash??
If there is an airplane accident, we can visualize how it crash more faster with "real evidence (video footage)" instead of speculating with Black Box recordings
I think it's time for Aviation Industry to add more innovative ways how to record a flight instead of just using Black Box (no visual)... They didn't want to spend some money to buy cameras and for its maintenance?

Many Emirates planes have external cameras that passengers can view on the inflight entertainment screens. However, I don't know if they record the footage.

A couple things I can think of - how is the safe operation of the aircraft improved by having a camera, are you going to transmit the video stream to some earthbound station or record it locally, how much would you say is reasonable to spend to certify and install theses systems on aircraft?

@selectstriker2 well, Aviation Company should be ashamed.. Then why Military Aircraft has camera recordings (like in cockpit) while Commercial Airplanes didn't have visual recordings

Well Aviation Company needs to stop being paranoid and super secretive. Just record every damn flight. What do they want to hide??? https://bradleygross.com/the-question-every-airline-needs-to-answer-why-no-cockpit-video/

Your understanding of a black box is deeply flawed. Modern black boxes (they're actually orange) record much more data than a camera could. The visualisations based on that data are not speculation. They're accurate reconstructions of the behaviour of the plane and include instrument and control position data that you simply couldn't capture with a camera.

This is a rant, phrased as a question.  At best, answers will be opinion-based.  Since Av.SE is not a platform for users' opinions (there are plenty of other forums for that), I'm voting to close this question.  (It's quite clear from the discussion in the comments above that the OP is far less interested in answers explaining the world as it is, than in voicing his opinions.)

The question is a bit of a rant and unfortunately this answer will be too.  I apologise in advance.
Suppose there was a SpaceX launch and the camera showed the explosion of the vehicle.  How would that camera's footage help determine the cause?  It wouldn't tell you if it was a leaky valve, a burst fuel pipe or a failed pump, for example.
A camera on the outside of an aircraft is unlikely to give you any information about why the aircraft crashed.  It may show damage but it won't show the cause of the damage.  It won't tell you how high the aircraft was, what the engine settings were, how the control surfaces were being operated.  Also, all aircraft would need to stream or record their video for that to be available to accident investigators.
The cockpit voice recorder and flight data recorder provide detailed and extensive information about the state of the aircraft before, during and usually after whatever incident occurred.  They provide real evidence and they are used to create an accurate and detailed represenation of what went wrong and why, it's not 'speculation'.  If a SpaceX rocket failed, the investigation would examine the pressurisation of the fuel pipes, the valve settings and the load on the pump, not the video footage.
As far as transparency is concerned, the International Civil Aviation Organization regulates commercial aviation and airline operators who fly between countries sign up to the Convention on International Civil Aviation (the Chicago Convention), article 26 of which concerns the investigation of accidents.  Notice that the investigation is carried out by the state where the incident occurred, not the manufacturer or the airline.
There are many reasons why commercial aviation is the safest form of transport, not fitting cameras to the outside of an aircraft isn't one of them.


text:
Are these two objects in cockpit of Antonov - AN 225 Mriya fans for air? What is their purpose?

In the above image, we can see two black objects that look like ceiling fans. This is just a reference image, but I am pretty sure that I have also seen small table fans mounted in cockpits of large cargo as well as high altitude flying planes with direction facing pilots in one documentary aired on tv.
Are they fans? and what is the purpose of their direction towards front glass in the pressurized air-conditioned cockpit?
Note - This question is not about FANS

For questions about something in an image, it usually helps quite a bit if you edit the image to draw a (red) circle around the thing(s) which you are asking about. Doing that makes it really clear what you are interested in, prevents confusion, saves people reading the question from spending time looking closely at the image to just find the thing you are asking about, and makes it less likely that someone answers about something other than what you are actually interested in. In other words: please edit the image to clearly indicate what you are asking about.

@Makyen - Yes done.

check this picture out https://www.reckontalk.com/wp-content/uploads/2018/09/Antonov-AN-225-world-largest-aircraft-15-cockpit.jpg

I am guessing, they are for when the ac is turned off for any reason. Or sunlight could be making pilots hotter than the rest. Also they don't have sheep skin seat covers. So maybe sweating was an issue for pilots even when ac was turned on. Although I don't know how a fan would help.

They are accessory propellers - to provide thrust for the ejector seats so that they can clear the massive tailplane instead of hitting it ;-)

@PoofosFoofus Humor is welcome, but it's kept to comments rather than answers. Your post would be deleted as an answer, but should be fine as a comment.

They are indeed "Soviet style air conditioning". You will see them in other Eastern-bloc aircraft too. We even had them in the Shorts Skyvan. They are operated by a simple on-off switch and can be swiveled to point in the direction chosen by the pilots. The fan blades are made of rubber so they won't cause injury if one's hand inadvertently comes into contact with them. In this picture of the Skyvan, you can see the fan (arrowed) and the switch (circled).

Here is another airplane with the ubiquitous Soviet Air Conditioning system, Tupolev 154.

I'm surprised that Soviet AC isn't a flap in the scuttle panel that can be opened for a draught, a-la Landrover series 4WDs.

They are just fans @SwiftPushkar, there for pilot comfort. They swivel so pilots can adjust them, there's nothing more to it than that.

I like the switch placed almost an inch clear of the blade path for operator comfort.

@SwiftPushkar: the pilot aims the fan so he or she has a nice cool breeze blowing on them. Yes, it sounds a bit odd - in an airplane flying at a few hundred km/hr the pilot wants a nice cool breeze. ??? But there you are... :-)

And when aimed at the glass, the air flow will help defog the window.

@mustaccio- That was exactly on my mind. But since I have seen many planes with wipers i haven't mentioned the point in question.

Technically it's not air conditionning. There goal is not to remove heat or moisture. There are fans whose goal is to increase comfort by nothing more than moving air.

That's why I put it in parentheses :) Those aircraft do have air conditioning packs.

They ARE fans, and they're just for pilot comfort.

authors: Bob Jarvis - Слава Україні


text:
Countermeasures taken to prevent reverse engineering of military fighter jet technology?
Inspired from this news  -
The immediate question  after reading the news will arose in the minds of novice people  like me that - How the aircraft manufacturers cope with this issue? Which leads to the main enquiry of.
What countermeasures are taken by aircraft manufacturers to prevent someone  from reverse engineering their parts ,systems , equipment , electronics or mainly material constituents etc.
Are there any other ways to  prevent  someone from reverse engineering military fighter jet technology ?
Note - I know there are various companies and thousands of components in a fighter jet , also  such a knowledge is the  trade secret of the companies. Considering that
the question didn't require a very detailed technical answer but  some basic  measures and   precautions that is best known  in  avaition industry in United States and   is  taken while either designing or exporting military fighter jets to other countries so that the material Constitution of components /parts , values of electronic components etc. remains a secret or hidden.

@ymb1 - No I am not expecting classified information and that is why  I said in question that "Best known to us or publicly known in Industry"  and is not  classified.

@ymb1 - Do you mean what measures were taken in past ? Like in cold war era etc.But I think the question will then become of history of design. I want to know the current solution , since the reverse engineering of military jets , helicopters by china is hot topic now a days.

Quite detailed related article: Military-Technological Superiority and the Limits of Imitation, Reverse Engineering, and Cyber Espionage

Step #1:  Don't let them get their hands on one...

Why I Voted to Close: This is a boat programming question. While it appears to be an aviation question, it is not really. The phrase "military fighter jet technology" could be replace with almost any other protected thing. For example, the US needs to protect submarine technology, so the need to protect proprietary technology exists. Suggest researching ITAR.

My guess is that to reverse engineer a part for something like a jet engine, the most difficult part is to get the material right. There are usually some pretty high-tech metals/alloys and they are usually cutting edge stuff so making a part that looks right may not be enough.

Yes that is absolutely correct. I am interested to know is there any way to hide material composition of engine or any other parts  itself like  a coating used as camouflage  or completely sealing the parts so that nobody can disassemble it.Or making some specialized tools for some parts so that only their technical team can replace/service them and are forbidden to be serviced by others.

You may be able to tell the composition of the metal used but to replicate it is not  simple as there are a lot of variables in the forging and treatment process. That itself is a show-stopper.

Yes , that is why it's tremendously difficult to manufacturer aircraft engines other than few companies , who have decades if experience and know how in the technology.

Correct. As was demonstrated by the Israelis when the Mossad stole the blueprints for the Mirage from the factory. They stole the specifications for all the custom alloys as well.

One of the best ways to prevent loss of industrial and national defense secrets is simply not to talk about them.  A hostile government cannot reverse engineer what it doesn’t know about.  Therefore it’s critical to keep the number of people involved or know about a project to a minimum.  Information sharing is limited to a need to know only basis, even to those who possess higher levels of security clearance higher than that required.  During the “black” days of the F-117 program, even the base secretaries had to hold at least a secret clearance, but had no idea the jet existed until it was declassified, simply because they didn’t have the need to know.
Quite often advanced R&D programs are located deep within pre-existing buildings used for commonly known programs of little significance, where foot and auto traffic are are indistinguishable.  So too, are classified infrastructure systems like computer servers and storage areas for classified engineering archives out of sight and out of mind.
But as G. Gordon Liddy once said, the only way three people can keep a secret is if two of them are dead.  Security slips do happen, either by accident or intentionally.  Limiting who knows what is an effective way to contain damage from a breach.  And the more you know the tighter the background checks and scrutiny of your life is prior to even granting you a clearance.  And things get hushed up.  Again during the stealth fighter program a shop worker on the floor became so enamored with a young lady outside of the company that he brought her plans of the jet to impress her.  The woman had the peace of mind to contact Lockheed, who merely fired the employee as opposed to pursuing criminal charges (I would have loved to have been a fly on the wall to hear the conversation between that poor guy and the FBI agents doing the exit interview!)
Specialized sites which deal specifically in “black” ie highly classified, compartmentalized programs are rare, but usually located in remote and inhospitable areas away from prying eyes.  They operate on specific schedules when spy satellites are not overflying and often in the dead of night to limit viewing.
UPDATE
In regards to capture and reverse engineering an aircraft by a hostile government, if the other side can get hold of an airplane intact and unharmed, there’s no reason they cannot carefully disassemble and reverse engineer the thing.  This has happened on multiple occasions  - soviets captured intact B29 and Rolls Royce Nene engines to reverse engineer into copies like the Tupolev TU-4 and Kilmov VK-1 respectively.  Sensitive tactical aircraft which are damaged and unflyable can be destroyed to prevent capture, as was the case of the as yet unidentified stealth helicopters used in the raid that killed Osama Bin Laden in 2011.
The biggest risks are in the form of aircraft sold or built under export licenses to foreign nations in good relations with the USA and its western allies which may also be open to selling the aircraft with nations hostile to the US and the west.  This can be done in the form of export and license production agreements between the United States and a country as part of an arms deal which prohibits sales of certain countries. Another method is downgrading the aircraft and onboard technology for export aircraft. This can come in the form of derated or inferior types of engines (the proposed F-16/79), inferior avionics, radars, and mission systems and even RCS size limits as seen on the F-35.  This allows a nation to purchase a fighter suited to its defense needs but is inferior in capability to the same type flown by US and western armed forces.

Yes your answer covers most part of hiding technology domestically from own people and competitors. But what about export versions which are physically present elsewhere? Also pls. take a look at my comment in one of the answers below.

@SwiftPushkar those tend to lack the most sensitive equipment and thus be less problematic when some potential adversary gets their hands on it. E.g. different engine, radar, lacking the ECM and ESM suites from the full version.

The Soviets didn't capture the Rolls-Royce Nene, they bought it directly.

Technically it was gifted to them

The simplest thing to do is not use the aircraft over enemy controled territory.
This is why the Gloster Meteor and early American jets deployed during the late stages of WW2 weren't allowed to fly over German occupied areas. The allies didn't want to risk them falling into German hands and the technology used to improve German jets.
Similarly early during the Korean war Sabres weren't allowed to fly over communist controlled areas for the same reason (though this was later abandoned when the MiG-15 appeared which was a rude surprise as it ate F-84s and F-80s for breakfast and was deemed both enough of a threat and at or near par with the F-86 that hiding the F-86 was no longer essential).
Of course this does rather limit how you can employ your superweapon, it is effectively only now useful for area defense and maybe as a standoff launch platform for longer range missiles. But there is precedent for it being done.
For much the same reason quite a bit of effort was employed during various conflicts to bomb crash sites in order to make the wreckage useless for intelligence gathering by the enemy. Sometimes it worked, sometimes (think the F-117 crash in Yugoslavia) it did not.

One technique that has been used in the past / is likely still used - are removable parts.
So when the aircraft is sitting at rest somewhere (including on your base) the "critical" parts are removed - think things like software, hardware crypto, comms modules, etc.  Yes, can't really use that to protect things like engines..


text:
Is there any clear picture or drawing, of a Wright brothers' plane, published before August 12, 1908?
Based on a video and two articles, one form May 1904, and the other from December 1951, both of them quoting people who personally knew the Wright brothers (see the explanations below), I have reached the conclusion that the oldest clear published photos of a Wright powered flying machine appeared in French newspapers on August 12, 1908, and the oldest unclear pictures in the Scientific American, on May 30, 1908. Another conclusion would be that the Wright brothers could not have taken any picture, at Kitty Hawk, North Carolina, of one of their airplanes in flight, before April-May 1908.
Question: Are there newspapers, magazines, etc., older than Aug, 12, 1908, that show a Wright airplane on the ground or flying? I am looking for them in archives but I can not find anything.

Video link: The Wright brothers and their imaginary 1903-1905 flights
The Wright brothers did not even finish the 1903 plane at Kitty Hawk, NC. Flyer 1 never flew as can be seen in the following 1904 article:
The Wilmington Messenger, Wilmington, North Carolina, May 26, 1904, col. 1, p. 6.

Elizabeth City Economist: A gentleman visiting this city whose home is
in Kitty Hawk, is responsible for the assertion that the Wright
brothers, of airship fame, will return to Kitty Hawk in the near
future and resume work on their aerial monster. According to this
gentleman the airship has never been removed from Kitty Hawk and
nearly all the interviews published in the papers of Norfolk have been
erroneous in this respect. This gentleman has assisted the Wrights in
all their work and has a general supervision of their property during
their absence. He says that they have not completed the ship and
that they will return some time within the next month and resume their
work. A story is current that they will complete the ship and make
the trip from here to St. Louis sometime this fall.

The text says that, according to a man that worked for the Wrights and took care of their things left behind at Kitty Hawk, the two inventors hadn't finished Flyer I as of May 26, 1904. In conclusion, this machine did not fly on December 17, 1903!

The true date of the above picture is May 1908 not December 17, 1903.
The fact that the photo was taken in May 1908 is also supported by the 1951 declaration of Alpheus W. Drinkwater, a man who knew the Wright brothers.

Wilbur and Orville Wright are credited with making their first powered
flight in a heavier-than-air machine on Dec. 17, 1903. But Alpheus W.
Drinkwater, 76 years old, who sent the telegraph message ushering in
the air age, said the brothers only “glided” off Kill Devil Hill that
day. Their ﬁrst real flight came on May 6, 1908, he said. (Source: New York Times, Dec. 17, 1951.)

As a note: The Wrights left Kitty Hawk, North Carolina, in December 1903 and only came back in April 1908.

resource location is off topic as defined by the help center

This is the definition of "Resource location":
" Where to buy a specific part, "Which headset is the best?", Where can I get a feed of flight-related data? " My question is about the history of aviation (an allowed subject) and has nothing to do with Resource location. Most questions in connection with the history of aviation can not be correctly and precisely answered without quoting old documents in archives.

I agree.  It is a good question.  I never knew there was any controversy.  And the doubts seem credible...

It's promoting a hoax, a debunked "conspiracy theory" type of revisionist history. One link to one ridiculous video is far from "credible" - there are Flat Earth videos with as much credibility as that. Let's don't taint AV.SE with this garbage.

At best this may belong on Skeptics.SE, but not here.

OK, I am all in favor of not propagating unrealistic conspiracy theories, but shouldn't we strive to debunk at every opportunity?  I had honestly never heard of this controversy before, but why not just answer the question with a link to the debunking?  Conspiracy theories thrive on being shut down without a reasonable counter...

@MichaelHall That's exactly the purpose of the site I mentioned, otherwise this is a debate here and not really well suited.

@Ron Beyer, I understand what you are saying and agree to a point, but the title question is really a simple yes or no question that could be put to bed forever easily enough for anybody stumbling on this site.  i.e. "Yes, and here it is: __" would kill the controversy forever, right?  Closing the question just adds fuel...

@RonBeyer, I found the same small article, that says the Wrights did not finish Flyer 1 in 1903, in: The Daily Free Press, Kinston, North Carolina, May 27, 1904, col. 6, pag. 1. (https://www.newspapers.com/ you can search for the article using the free trial option). If the Wrights flew in December 1903, such articles should not exist. Forget about the video (also it contains interesting pictures in French newspapers, I have never seen before). Both the May 1904 and Dec. 1951 articles are authentic. There is no conspiracy theory here. They are not written by the Flat Earth people.

Re - "The true date of the above picture is May 1908 not December 17, 1903."-- that's ridiculous.  Why has this question not been heavily dv'd?

Dozens and dozens, or more likely hundreds, of blatantly false accounts of the Wrights' activities may be found in the newspapers of the time.  And the point is?

@quietflyer , There is only one contemporary false account (denied by the Wrights on January 6, 1904) for the interval of interest 1903-1905. It is an article that claimed the 1903 machine flew 3 miles and had a propeller placed under the plane and another behind the wings. The story propagated in the newspapers across the US. This is the article: “Flying Machine Soars 3 Miles in Teeth of High Wind Over Sand Hills and Waves at Kitty Hawk on Carolina Coast”, Virginian-Pilot, Norfolk, Dec. 18, 1903, col. 7, pag. 1. (www.loc.gov/resource/mwright.05001/?sp=12).

@RobertWerner -- thanks for setting me straight.  My impression was very different, based I guess on faulty recollections of things I had read some years back in books about the Wrights.

Related --https://aviation.stackexchange.com/a/86778/34686 , https://aviation.stackexchange.com/a/81263/34686

I am not aware of any picture printed before August 1908 and showing a fully recognizable Wright plane, beyond any doubt.
As a remark, there exists a drawing, published in L'Auto, a French newspaper, on December 24, 1905, but it is just a rough sketch. However, this caricature is the closest drawing to what would become to be known as the Wright planes, much later, starting with August 1908.
As an explanation: Robert Coquelle, a French journalist, while in the United States for other purposes, visited the Wright brothers, did not see any plane and once back in France he made fun of them in L'Auto in an article titled: "The conquest of the air by two bicycle dealers". Coquelle does not clearly explain the origin of the drawing below that illustrates his article.

The true aeroplane of the Wright brothers.
Source: 1905-12-24, Robert Coquelle, “La Conquête de l’Air par deux Marchands de Cycles. Comment un ancien champion cycliste, Johanny S. Johnson, introduisit un rédacteur de « l’Auto » dans l’atelier des frères Wright.”, L’Auto, Paris, Saturday, December 24, 1905.

Funny article, funny subtitles: "An 1 hour and  40 min flight ended with a rapid descent amid little black pigs. Doubts are no longer allowed!". (Source: https://www.loc.gov/resource/mwright.05001/?sp=34).

Related -- https://aviation.stackexchange.com/a/77074/34686

So all the photos from https://www.wright-brothers.org/Information_Desk/Just_the_Facts/Airplanes/Flyer_I.htm (linked in the linked Q) are fake or antedated? I see this Q seem to asking about published pictures, so I guess what the Q really meant is when those were published.

Are you seriously concluding that the Wright brothers did not fly until 1908 based on the absence of a published picture and a couple of outlier statements?
In the past, it has been all too easy for someone to pull a couple of articles out of the air and assert that our understanding of history is wrong. However, in the age of the internet, this is no longer true.  If you go to Chronicling America a free newspaper database and search for "Wright brothers" for the period 1903 to 1908, you will get thousands of hits. If you search for the period 1903 to 1904, you will get hundreds of hits describing the 1903 flight.
For example, a 1907 article called "The Reality of the Airship" which appeared in the Sunday Star, Washington, DC (6/2/1907), part 4, p. 4, quotes at great length a speech given by Sir Alexander Graham Bell - a competitor to the Wright brothers. He states "Their machine has flown not once simply, but many times, and in the presence of witnesses, so that there can be no doubt that the first successful flying machine has at last appeared." He then describes the Dayton flights in great detail.
Given all those contemporary articles and eyewitness accounts, I believe that the burden of proof is on you to prove that all those statements were lies before you can seriously assert that the Wright brothers did not fly until 1908.

It’s worth bearing in mind that photography in 1903 was only a small step away from having a portrait painted and was ill-suited to a transient event with significant movement.  It might be considered analogous to questioning whether a present day event took place because it wasn’t enshrined in a non-fungible asset.

After searching "Chronicling America" for a few months, I have reached the conclusion that there is nothing there of any value regarding the 1903-1905 powered flights of the Wright brothers. The most accurate and documented articles repeat again and again the stories launched by the Wright brothers themselves. Alexander Graham Bell just read "The statement of the Wrights to the Aero Club of America (dated March 12, 1906)" in which the two inventors claimed a number o long flights seen by 18 witnesses, all named. (see: https://transcription.si.edu/view/13664/NASM-NASM.XXXX.0376-M0000104-00020).

Phil Crowther, I am still waiting to see  that "clear picture or drawing, of a Wright brothers' plane, published before August 12, 1908". I was unable to find it in the archive "Chronicling America".

Regarding the the absence of a clear drawing, I am a bit confused because in your previous post, you showed the drawing published in 1906.  While not a work of art, it does clearly show the basic shape of the airplane, the propellers, chains and track they used.  Their reluctance to publish the 1903 picture in 1903 is understandable because they were attempting to patent their wing-warping mechanism and would not have wanted the public to see the mechanism until the patent was granted.


text:
Does a diesel piston engine's power decrease more slowly with altitude than with an AVGAS engine?
I have a power-altitude curve of the Austro Engine AE-300 provided by manufacturer and I don't know the reason why power decrease lower than other engines. The curve is in the end of the pdf in this link: https://austroengine.at/uploads/pdf/mod_products1/AE300_Technical_Data_Sheet.pdf

Welcome to the community! Because the Austro Engine AE-300 is a diesel engine,(JetA/Kerosene and Diesel are very similar) it is equipped with a turbocharger.
Turbochargers compress the engine's intake air to maintain Sea Level air density so that the engine produces full power as you climb into less dense air.
Speaking of car and truck engines, diesel engines are often equipped with a turbocharger to increase the intake air pressure.
On cars and airplanes both, gasoline piston engines are not usually equipped with a turbocharger unless the engine is installed on a high performance car or aircraft where the customer is paying more money to get more performance.
In recent years, some cars that are not high performance cars have been equipped with turbochargers to get more (an average level of) performance out of a very small engine.
Turbochargers are very useful for aircraft since they fly up into altitudes where the air becomes less dense, reducing performance.
When flying a non-turbocharged gasoline engine airplane the loss in engine performance becomes quite noticeable when climbing through 5,000'. If it is a hot day with a high density altitude the performance loss will occur at an even lower altitude.
An engine not equipped with a turbocharger is called "naturally aspirated", meaning that it is "breathing" naturally, not with a turbocharger forcing air into it for better performance.
An interesting thing to note about the Altitude Performance Graph you linked to is that they are comparing their AE-300 turbocharger-equipped Diesel engine to the Lycoming IO-360.  The Lycoming IO-360 is not turbocharged.
The turbocharged IO-360 is called TIO-360 (T= Turbocharged, I= Fuel *Injected, O = Opposed (Horizontally opposed engine design).
The non-turbocharged IO-360 is the equivalent, typical and common General Aviation engine to compare the AE-300 to, in terms of horsepower and performance, but it does not have a turbocharger.
Therefore, when you climb into thinner air the engine gets less oxygen and creates less power, resulting in the altitude performance drop-off in the chart you linked to.
Based upon the linked Austro Engine chart, I think your question is about General Aviation propeller aircraft in which the propeller is driven by a piston engine, not about turboprop engines where the propeller is driven by a jet turbine, is that correct?

I strongly suggest editing this answer a bit. Diesel engines do *not need any kind of forced induction to function, the pressure required for ingition is achieved by high compression ratio. The reason most of them are equipped with FI, is that they are incredibly sluggish if naturally aspirated, and as such unsuitable for aviation use and many other applications as well.

...and the use turbo chargers is by no means restrected to high performance gasoline cars. I've driven turbo charged gasoline cars that were desparately sluggish.

@Jpe61 My intuition told me not to type that diesel engines required turbochargers but I did it anyway. :)  I will change it.  What was the slow turbo car that you drove?

Many actually, vag group specializes in poorly performing small turbo cars  their lineage of barely over 1 liter tsi/tfsi engines is just hideous.

I thought essentially all auto engines nowadays were turbocharged?

@Vikki, I haven't kept up with the specs of current autos in the last 12 years. To my knowledge turbos (and their additional cost and complexity) have historically been used on gasoline engines to increase performance.  As Jpe61 mentioned, VW group has used them on low-power engines, likely to get more horsepower out of a small engine (which likely improves fuel efficiency). Years ago I test drove an ecoboost Ford Focus with a very small turbocharged engine that shut off when you came to a stop and then restarted itself when you hit the gas.

Also note that turbochargers don't necessarily maintain sea level pressure.  At least in automotive use (not that familiar with aircraft ones) they create an over-pressure of 6-8 PSI at sea level, and can maintain that 20-22 PSI intake pressure up to some considerable altitude.

@jamesqf The overpressure that turbos create on a car engine is the reason I want to add one to my Nissan 240SX!

The important part is not that the engine is turbocharged, but that it is flat rated. That is a property independent of turbo-charging, though nobody flat-rates a normally aspirated engine (non-turbo-charged), because it makes basically no sense. But a turbocharged engine does not have to be flat rated.

@Jan Hudec, I understand your comment to mean that the AE-300 is flat rated because it is turbocharged. Because "nobody flat-rates a normally aspirated engine (non-turbo-charged), because it makes basically no sense". Am I understanding correctly?

@JetCityMatt it's not a strict implication. It is flat-rated, because that power curve is most desirable they can get for engine weight and efficiency, and being turbo-charged is precondition for that.

@vikki not quite, for example Mazda is still firmly settled in naturally aspirated engine development with the Skyactive engine family. And in US there is a plethora of NA engines both in production and development. All diesel engines are FI these days though.

@Vikki: Europe has strict environmental regulations that favor turbocharged engines. As Jpe61 notes, in the US gas is cheap and regulations lax, so NA engines are still relevant there.

It is not because it is a diesel engine, though diesels are more likely to be designed that way.
The engine is so called “flat rated”. That means its power is not limited by simply not being able to burn any more fuel at given piston volume and RPM, but by the peak pressure or temperature.
The controller limits the amount of fuel that can be injected at density altitudes below 9000ft to prevent exceeding those parameters and damaging the engine. Without that the power curve would have the same slope as for the IO360, but the engine would have to be much heavier.
But you don't actually need that power at low altitudes. Drag is the same at the same indicated airspeed, you need the same thrust to maintain your optimal cruise speed at any altitude. But power is thrust times velocity, i.e. true airspeed, so at higher altitude you need more power to maintain that indicated airspeed. So by flat-rating the engine it can allow cruising higher without making it much heavier.
Now diesel engines are more likely to be flat rated.

Only turbo-charged engines tend to be flat rated. Flat rating basically means limiting the manifold pressure. But the ambient pressure can always get into the engine and the engine always has to withstand that. So the limit is always higher than ambient pressure, which can only occur in turbo-charged engines. There it is also possible to protect the engine from exceeding the manifold pressure limit by adding appropriate waste-gates in the turbo-charger.

Diesel engines are more likely to be turbo-charged. Diesel engines inject fuel only at the point it should start burning, so they can have high compression ratios, and in fact need high compression ratios to reach the auto-ignition temperature of the fuel just by compression. On the other hand spark-ignition engines have the fuel already mixed in the air, so they must not reach that temperature, which limits their compression ratio. And turbo-charging increases the effective compression ratio, so spark-ignition engines can only be turbo-charged so much as the intercooler can prevent the temperature getting too high, while diesels can be turbocharged as much as the cylinders are built to handle.

So because adding turbocharger increases the power with less weight than making the engine bigger, all diesels are turbo-charged these days and have been for quite a while. And adding a bigger turbo to an engine is relatively small change that allows pushing the maximum power to higher density altitude, so once the engine is turbo-charged, it's the logical next step.
I would add that the big aircraft engines of 40s and 50s were all flat-rated, often to over 15,000 ft. I.e. their power curve had similar shape to what they show for the AE300 even though they were spark-ignited engines.
E.g. the huge Wright Cyclones were limited to 54 inHg manifold pressure for take-off and 49 inHg manifold pressure continuous, but they'd go well above that if you firewalled the throttles at sea level. And they had a second stage turbo-charger that the flight engineer only turned on above around 8,500 ft. At the time there were no electronic engine controllers, so the crew had to pay close attention to the manifold pressure gauge to avoid damaging the engines.

Flat rating is a term used with turbine engines

@Koyovis and do you have a better term for piston ones? The principle and reasons for it are exactly the same.

It usually means a higher max power turbine engine delivers restricted power. The turbo- and supercharged piston engines just deliver max horsepower until the turbo cannot maintain zero altitude intake pressure anymore. So yeah, the power delivery curve is flat for the first bit, not because of power restriction though.

@Koyovis, the turbo- or super-charger output pressure is proportional to its input pressure, so if you were allowed to open the throttle wide, it would produce more power still at lower altitude, it would just blow itself apart soon. It is just as much restriction on the piston engine as it is on the turbine that does not let you request more power from it at low density altitude.

Yes. Please note that I am not arguing with you.

It's all about the air compression!

The graph that you mention shows two diesel/jetfuel geared piston engines, and one avgas direct drive piston engine, the Lycoming IO360. The two diesel engine graphs have a horizontal slope at lower altitudes, which is indeed caused by an intake air compressor.

D - Direct Drive
G - Geared (between prop and engine)
N - Normally Aspirated
S - Supercharged
T - Turbocharged
C - Carbureted
I - Fuel Injection

The figure above is fig. 4-7a from Torenbeek, Synthesis of Subsonic Airplane Design, and compares different configurations of carbureted avgas pistons engines at constant piston displacement. As can be seen:

only the normally aspirated avgas piston engine (like the Lycoming O360) has a continuously decreasing performance with altitude;
the Geared Turbo engine has the best altitude performance, highest power at any altitude.
the Direct Drive engines are limited by lower RPMs due to the propeller max RPM.

The interesting bit of the graphs is what happens to the right hand side: they all disappear into 0% at 16.5 km altitude. So the higher the initial power at 0 km, the steeper the decline into zero at 16.5 km. And I believe this is basis of the OP question.

The Lycoming O360 is a 6 l normally aspirated direct-drive engine and develops 180 hp @ 2700 rpm.
The AE300 is a 2 l turbo-charged geared engine, 168 hp kW @ 2300 rpm prop
The Thielert/Continental Centurion is very similar to the AE300, with a lower certified power output.

So the question is indeed: why do the diesels not follow the general trend shown in the Torenbeek graph? This is because of the better thermal efficiency of a modern diesel engine with common rail injection:

The compression ratio is higher than that of an avgas engine: diesel has no knocking effect at high compression. Avgas engines using high octane fuel (100/130) can use compression ratios of 1:8 to 1:10, the AE300 type engine has a compression ratio of 17:1. So at whatever altitude, the surrounding air pressure is increased more in a diesel engine than in an Avgas engine.
The diesels have fuel injection, which results in more efficient combustion. Fuel injection increases power output at any altitude by a few procent.


text:
Why doesn't critical angle of attack increase with airspeed?
Critical angle of attack is related to the Coefficient of Lift, which is a function of Reynold's number. Reynold's number depends on the speed of the aircraft. So why doesn't the Critical Angle of Attack change with speed?
Update: My current knowledge about this topic comes to this- The Critical Angle of Attack is a constant for an aerofoil at any altitude and speed. CAoA depends upon Reynold's number, which itself relies upon the velocity of the airplane. For the CAoA to be nearly constant, the effect of Reynold's number and the velocity has to be negligible. Is my understanding correct? If so, why is what I mentioned the case?

@Bianfable I think this question is sufficiently specific that it is worth a more direct answer than that.  Peter does mention Reynolds Number once in the answer, but without any explanation of how much effect it has or why we tend to ignore that & talk about "the" stall angle of attack as if it is perfectly constant.  If anything, the remark in that answer validates the premise of this question, without really answering it.  Voting to leave open.

Seems to be the same question than Does airspeed affect the critical angle of attack on an airfoil?, and the answer is yes, so your premise is false.

@mins I had come across that post. Rafael Morrilo's answer to that question speaks about the pilot's perspective. How does that differ from AEhere supports Monica's answer? Could you please help clarify the difference? Also, the answer which Bianfable linked to speaks about how Reynold's number has little effect on the CAoA. I assume that corresponds with AEhere supports Monica's answer? If so, why is it ignored?

@mins, Rafael M. says "My point is valid from this (the pilot's) perspective, where the pilot needs to know that he can stall the plane at any speed or altitude at a specific AoA." That implies that the Critical AoA is the same at all altitudes and speeds. Am I misinterpreting this? This is from the pilot's POV. So, what's the explanation for that? Also, how does "pilot's perspective" differ from "design perspective?" I'm not very well versed. Does it simply imply that it just doesn't matter from a pilot's perspective as it's negligible? That would bring us back to why it's ignored.

@mins However, also I came across this, in a guide by the FAA: "The critical AOA is an
aerodynamic constant for a given airfoil in a given configuration. The velocity of the relative wind does not matter; the airfoil will ALWAYS stall when the critical AOA is reached." Now I'm confused by the contradictory answers given by the FAA and AEhere.

Let us continue this discussion in chat.

@RalphJ Good call, we received a much more detailed explanation now. Retracting my close vote...

@AlphaRogue The dependence is small. It can mostly be assumed to be constant. If the quote above doesn't include the velocity in the "configuration", then it assumes a reasonably small change with it. Very likely only assumes subsonic flight and quite likely well below transonic. Also, transients are another issue that can change when the airfoils stalls and that statement is silent about them.

Your scepticism is justified. The critical angle of attack (cAoA) can grow as well as shrink with increasing airspeed. Growth is generally due to a higher Reynolds number while a reduction in the cAoA with increasing speed is a transsonic effect, so it depends on the flight Mach number.
In one peculiar case this already stated to happen at Mach 0.3, far below what is normally considered transsonic.
But let's start with Reynolds number effects first.
Frequent readers of my answers know that at this point I turn to Sighard Hoerner's book Fluid Dynamic Lift, and you will not be disappointed this time. In section 4, starting on page 4-12 of the 1985 edition, you will find several plots summarizing lots of test data. Hoerner uses c$_{lx}$ to denote the maximum lift coefficient, and although the lift curve slope increases a bit with Reynolds number, this effect is small when compared to the delayed separation happening with higher Reynolds numbers, so his data implicitly shows that cAoA is generally increasing with speed.
Here is Figure 18, the plot for airfoils of 12% relative thickness:

The sudden jump at Re = 0.7$\times$10⁵ to 0.9$\times$10⁵ is caused by earlier transition with higher speed, so a low cAoA caused by laminar separation below that Reynolds number is replaced by an earlier transition and delayed separation of the now turbulent boundary layer beyond that Reynolds number. But this is the realm of small model airplanes.
The highly cambered Joukowsky airfoil goes against the trend and shows a reduction in maximum lift between Re = 10⁵ and 10⁶. The same happens for airfoils with a relative thickness exceeding 20% and is caused by their large nose radius. Hoerner writes:

The airfoil nose-radius ratio is thus an important influence with regard to the critical Reynolds number of the section, figure 17. Note that the sections with the smallest curvature tend to have the highest critical Reynolds numbers for the strong increaseof c$_{lx}$.

Those are the ones at the bottom of the group.
If the lift curve slope of a 2D section is 2π, the increase in c$_{lx}$ between Re = 10⁶ and 10⁸ from 1.2 to 1.9 is equivalent to a typical increase in the cAoA of more than 6°. Subtract one degree for the increased lift curve slope and you still have a change of 5° when a typical cAoA at Re = 10⁶ in 2D flow is 12°. In reality, such a range of Reynolds numbers would mean a speed ratio between slow and high flight speed of 100. More realistic ratios are 4, so the change in cAoA over the typical speed range is rather small.
Now to the influence of the flight Mach number:
Again, Figure 27 is one of a group which plots c$_{lx}$ over Mach, see below.

NACA 64-210 shows a dramatic drop above Mach 0.2, so why would I blame this on transsonic effects? Thin airfoils with small nose radii show very steep suction peaks at the nose close to stall, so here the local Mach number becomes indeed supersonic while the flight Mach number would make you neglect compressibility effects. Hoerner writes:

On the first tenth of the chord on blunt airfoils, standing shock waves are formed similar to the more well known shocks on the aft section of the airfoil, except their size is an order of magnitude less. The familiar lambda type shock with a weak forward shock and pressure plateau as illustrated in figure 26 is formed with a laminar boundary layer. With a turbulent boundary layer, the single shock with a strong pressure rise and an expanding bubble is formed at the nose (25,b). These shock waves interact with the boundary layer, causing separation and a reduction of c$_{lx}$ as illustrated in figure (27).

If you want to read my explanation, please turn to the second part of this answer.
Now the change in cAoA, given the right airfoil, can be rather dramatic over the realistic speed range of a fast airplane, so it should not be neglected.
And last, the peculiar case hinted at above: I once worked on a jet trainer which I predicted to have a maximum lift coefficient in clean configuration of 1.28. Flight testing later revealed that it could achieve a maximum lift coefficient of 1.35 near the ground but only 1.26 at 4000 m. The drop in air temperature between ground and 4000 m would shift the Mach number up and cause shock waves at the nose which were not present (or less pronounced) near the ground.

"The critical AOA is an aerodynamic constant for a given airfoil in a given configuration. The velocity of the relative wind does not matter; the airfoil will ALWAYS stall when the
critical AOA is reached." - FAA guide. Could you please explain this statement?

@AlphaRouge it seems to be undergraduate "kindergarten" vs doctorate level understanding.  The bottom line seems to be:  Reynolds number will not change enough within the flight envelope of a given aircraft.  Keep in mind this envelope does not start at 0, every heavier than air craft has a minimum flying speed.  In the case of the 172, that's around 50 knots, with Vne around 3x more.

“the lift curve slope increases a bit with Reynolds number” - Is there an explanation for why this is the case? My intuition tells me it’s something to do with the boundary layer, but I can’t be sure. (I did follow the link, but it seems that it’s temporarily offline)

@Wyatt Your intuition is correct, see here for an explanation. At a higher Reynolds number, the boundary layer is thinner especially on the suction side and has less influence on the effective angle of attack.

@PeterKämpf Ah I see. Thanks for helping me clear that up. (The linked answer was actually to a question that I had asked!)

Yes
One way to gain greater understanding is to go to airfoil tools and observe the lift vs AoA of your favorite airfoil (try the Clark Y for starters) and you will see that Reynolds number effects generally occur across several orders of magnitude, well outside the speed envelope of your aircraft.
A bit like saying from 0 to Vne would be a few centimeters on a 1 meter Reynolds scale.  Reynolds number is linearly proportional to V (not V$^2$), so only great Velocity meters/second (and chord in meters) changes will make a noticeable difference.

Reynolds Number = Velocity × Chord/1.48 × 10$^-5$

Reynolds number, and therefor stall AoA, can be considered approximately the same within a given aircraft flight envelope (recreational, low subsonic), with manuvering effects (G loading in turns) being much more critical.

Is Yes an adequate answer to a why-question?

Only if it's obvious.

I think the short answer is mostly sufficient as well. Certainly no reason to downvote in the slightest, just because a more thorough answer apoears later. But for aerospace the kinematic viscisity cannot be assumed to be constant at en exact value of 1.48e-5. Either the exact value is not too relevant and we just use a symbol, or the exact value is relevant, but then the temperature dependence will come up as well.

@VladimirF noting from the Joukowsky airfoil data above one might notice the relationship to curvature and camber to airspeed.  With a heavily curved wing at higher V, it seems Clift breaks down a bit due to earlier onset of flow separation, which seems to be a mass and viscosity issue.  So, rerunning the data plot in say CO2 (like Mars) would be interesting.

authors: Vladimir F Героям слава


text:
Why don’t gliders use swallow tails?
I’ve always wondered this. Why do gliders use a T-style tail, as opposed to a V-tail ie a swallow tail design?  I think it would represent a significant reduction in weight over a conventional empennage, not to mention, offering a reduction in drag.

Because the swallows needed them and would not give them up :)

The V-tail was a trend in glider design between the late Fifties and the early Sixties. High-performance gliders like the HKS-1, the Arlington Sisu 1A$^*$, the SB-5, the Standard Austria or the Schempp-Hirth SHK had them, as well as the aerobatic H-101 Salto.
However, eventually the T-tail became the preferred choice for these reasons:

The endplate effect of the horizontal allows to make the vertical about 20% smaller.
A T-tail will suffer the least damage in an outside landing.
The effectiveness of a V-tail is lower for the same area, especially in damping.
V-tails are not really better in terms of drag reduction.

$^*$ Added thanks to the helpful advice by Thomas Perry.

A friend had an Austria glider with unusually large all-flying V tail surfaces and anti-servo tabs. He said it was actually deficient in rudder authority, making it a challenge in x winds.

@JohnK Name me one glider which isn't deficient in rudder authority at low speed. They all are, more or less. Fly fast enough and things become fine, though.

@PeterKämpf  ...and I am going to add, the enigmatic Sisu 1A, if that is ok with you...

@ThomasPerry: Thank you, that is a very welcome addition!

@PeterKämpf  Thank you, Peter.  Your acknowledgement is very kind.

@ThomasPerry ... and well deserved. I had no prior knowledge of the Sisu 1A.


text:
What happens to the assumption ∂p/∂y≈0 in the region of separated boundary layer? is it still valid?
I am reading about Boundary Layer(BL) and seems that in the derivation of the governing equations there is an assumption that the pressure, $p$, in $y$ direction is constant, that is:
$${\partial p \over \partial y} \approx 0$$
regardless of the $x$ location.
However, I am already wondering how valid is this assumption when the boundary layer separates.
Is that assumption valid for both Laminar BL and Turbulent BL?

It's possible to derive the condition you mention from the Navier Stokes equations (for example here). which assumptions are needed to get to this point?

I am not sure but this won't be valid because pressure changes in separated flow


text:
What are the standard numbers for fuel consumption (kg), kg/NM, and kg/h, of Boeing 737-300?
I'm currently working on a school project regarding the analysis of Boeing 737-300 fuel consumption. I'm working on some parameters that my supervisor gave me, which are :

Total fuel consumption (kg),
Fuel consumption per Nautical Miles (kg/NM), and
Fuel consumption rate (kg/h)

I'm curious if there are specific informations in the industry, or from OEM, or from the manufacturers, regarding the standard of the numbers of these parameters from B737-300 flights, official/reliable references in essence, so i can use them for benchmark to my calculation results
Been searching for lots of reliable references that i can use before, but the best i can find are forum posts with a rough number, or some random aviation websites, and i'm not quite convinced to use them as my benchmark/reference in my report

There are charts out there, but the rule of thumb is 5,000 lbs per hour average for a flight. The first hour is more given the higher fuel flow at takeoff & initial climb, but as an average that's a reasonable ballpark.
If I need more precise values, I'll either look at the fuel flow gauges in the engine instruments (for an indication corresponding to the present conditions), FMC fuel projections (which is computed burn from now until landing), or I'll have a dispatcher generate a computer flight plan (for cases like determining the burn to get to a particular alternate, or if we operate a flight at a different altitude or using a particular route).
If you need for specific numbers, others may be able to provide charts that consider aircraft weight, flight altitude, and temperature, but for a first approximation, 5,000 pph works fairly well for most cases.

You can look at the appropriate airport planning document.  Airline manufacturers make them available.
It contains a ton of information, you'll want to check out the payload-range diagram.  For the -300, it is on page 69 of the above document.
In particular, you'll want to check out the slanted lines labeled by their break release gross weight.  The negative slope of these lines is the specific range (nmi/lb) of the aircraft.
You may be able to search around for a pilots operating handbook (POH) that will contain more details.  Unfortunately, the chapter of interest (aircraft performance) is often left out of the POH's available online.


text:
What is the flight attitude of a Partenavia/Vulcanair P68?
Planning to fit a camera into a Partenavia P68 for vertical (nadir) imagery, and would like to know the difference between ground and 'normal' flight attitude within 2-3°.
I'm a pilot, and familiar with mainly with Cessna 172/182/206 official flight attitude (i.e. levelling point above the door, or by screws on fuselage) - seems like, in comparison, P68 sits on the ground in pretty much the same angle as it would be in flight, but can't find any confirmation of this.
What is the normal levelling line used? (While attitude can certainly vary with W&B, airspeed and flaps used, I'm interested for now in the 'official' levelling you might find in the POH)

How critical is this, what is the tolerance you need to achieve?

Attitude varies in the same airplane depending on weight, balance, and airspeed. There's no single answer.

If I needed a constant nadir direction for a project, I'd just use a gyro stabilization system, this can be rented and there are cheaper devices.


text:
What is the maximum roll rate for an RC aircraft of low maneuverability?
I'm a student of mechanical engineering and my graduation project is basically an RC aircraft powered by a propulsion system and It is used for general transportation. The aircraft doesn't require much maneuverability. The problem is that when I was designing the ailerons using the design equations included in the reference 'Aircraft Design  A Systems Engineering Approach by Sedraey', the roll rate calculated was roughly 12 rad/sec, which is probably a large number for an aircraft that doesn't require much maneuvering.
My question is of course a sanity check; is this roll rate reasonable ? because I used MATLAB for optimization of the geometric parameters of the aileron and the output geometry seemed logical when I visualized on SOLIDWORKS.
Update : I looked up other reference which are specialized in aircraft stability and control and I have finally managed to get reasonable results.
From my experience I would never recommend using 'Sedraey' as a reference for learning about aircraft design.
Thank you all for helping me.

I’m voting to close this question because it belongs on Drones.SE.

Something is wrong in these formulae. How do they willy-nilly assign [m/s] to $y_D$, while it is clearly just [m]? If $L_A$ is the roll moment from ailerons ([N m]), then (12.37) will indeed be [1/s], but 1) randomly picking "drag moment arm" at 40% while the main resisting force, roll damping, is proportional to the square of wingspan, seems wrong. And 2) this $L_A$ will decrease with the roll rate (simply because the local angle of attack will partially negate aileron deflection). Very suspicious source.

Roll rate will be dependent on the airspeed.  A model airplane will generally be flying at around 20 knots.  The V$^2$ is used to calculate the roll torque based on the lift difference of aileron up and down.  Roll rate stabilizes when drag torque equals roll torque.  Weight placement in wings is also critical.  1 radian per second is more like it.  Comparison with existing R/C models may be helpful, as would speaking with their pilots.

I agree with you that these equations are quite suspicious. It would be helpful if you referred me to a better resource, especially if it is related to RC airplanes. @Zeus

I think talking to RC experts and pilots would give me a better insight and intuition. @Robert DiGiovanni

@RalphJ In my opinion, just because it's related to model aircraft, doesn't disqualify a question from here. This is a theoretical design question, which has more to do with aviation than with the practice of specifically drone use.

Can you share how you get the proper formula and results I was also referring to Sedraey for all the calculations of high-lift devices.

Twelve radians is nearly two full turns -- per second!
I've got a couple hundred hours of stick time in R/C, ranging from two-channel sailplanes to four-channel mildly aerobatic sport models.  The most aerobatic models I ever had, a Swizzle Stick and a Terrier, had a lower roll rate than you propose; few pattern aerobatic models have higher (maybe a Zlin or Cap-21 -- and maybe not).  Two rolls in a second is asking to become disoriented, which leads to "planting balsa trees" (an old phrase when I flew in the 1980s, perhaps obsolete with modern materials and methods).
If the main goal is to fly like a transport aircraft -- that is, mainly wings level, just enough bank to make turns to stay within sight and control range -- you could do very well with a fourth that roll rate and probably get away with an eighth.  However, I'd recommend you build to have at least twice the control authority you believe you'll need, and adjust your control throws near their minimum for maiden flights, then increase them once you know what's needed.  Also strongly recommended is to have an experienced pilot at least do the first takeoff and hand over the transmitter once you have some altitude, especially if you have little experience flying R/C aircraft.

Thanks you for taking the time to reply to my inquiry. I know the number doesn't seem reasonable. I was wondering if this number is a result of any mathematical error I could have made and probably I didn't pay attention to. But I guess from your reply you mean that the issue can be solved if I informed the pilot with this high roll rate and that the aircraft still maintains lateral stability, right ?

I certainly wouldn't want to try a first takeoff with 12 radian/s roll rate unless I also had exponential control in the transmitter (that was a very expensive option when I flew a lot).  Then again, I used to set up my control throws with "TLAR" rule -- That Looks About Right -- and all my models flew very well.

Well then if I wanted to redesign the aileron so that I can achieve a decent roll rate, what is the first thing I should look at ?

I'd start with control throws.  A reasonable size aileron can produce hyper-roll rates, or easily controllable rates, depending on how many degrees it's deflected.  Control throws can also be easily adjusted (on the ground, or in flight with some radio sets) to give transport or aerobatic flight characteristics.

I will definitely talk to the pilot, and he has to be a professional one, and see how we can probably solve this issue. Thanks alot @Zeiss Ikon